Hazards of Chemicals and GasesDOE-HDBK-1015/2-93COMPRESSED GASESRev. 0CH-05Page 27When some gases come in contact with certain other substances, spontaneous ignition mayoccur. One of the better known of these reactions is that of oxygen with oil. Another reactionis the possible ignition of hydrogen due to the heat of the reaction which liberated it, such assodium in water. Additional sources of ignition are as follows.The spontaneous ignition that may occur in oily rags and other materials.Smoking is a principal cause of fire, and calls for strict prohibition in hazardousareas.Other sources of ignition include sparks or flame-producing operations such asgrinding or welding, and equipment such as heaters or boilers.Ferrous handtools can produce a spark when struck against, or by a suitableobject, and may cause ignition of some gas-air mixtures.Other possible sources of ignition are internal combustion engines and battery-powered electric vehicles.The most disastrous accidents involving industrial gases have been caused by ignition of gas-airmixtures. Fires cannot occur without three essential factors being present in the right quantity,at one place, and at the same time. These factors are fuel, heat, and oxygen (which is normallysupplied by air). When they are present in the same place, in the right amounts, and at the sametime, there will be a fire. To prevent a fire, it is necessary to keep only one of these factors awayfrom the other two. Air is necessary for life and cannot normally be eliminated, but the fuel andheat can be kept separated. Proper operational and maintenance procedures will help preventa flammable gas from escaping into the air, but because this is always a possibility, it is mostimportant to eliminate the source of ignition.SummaryThe important information in this chapter is summarized below.Compressed Gases SummaryThe following terms are defined:Compressed gas is defined as any material or mixture having in the container anabsolute pressure exceeding 40 psi (pounds per square inch) at 70 F, orregardless of the pressure at 70 F, having an absolute pressure exceeding 140 psiat 130 F; or any flammable material having a vapor pressure exceeding 40 psi at100 F.
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